UPDATE: If you don’t want to read the source code of the Let’s Encrypt tool you’re using, you might as well use the official client, that does a bit more magic. Don’t get me wrong, the official client is open source, too. But it has way more lines of code, so it’s harder to read through. The Hiawatha user VirginSteele posted a four-step tutorial here (scroll down to the entry with the timestamp 12 November 2015, 14:43). One notable difference is, that you don’t need to stop the webserver there, as the letsencrypt-nosudo script I’m using in my tutorial can’t do this yet.